It's not really a Physical Sweeper due to the lack of Physical moves Mewtwo can learn. It has a very limited Physical Movepool. You lose Psystrike and Psychic, and get only Zen Headbutt and Psycho Cut for Psychic Stab. As for Fighting STAB, you really only get Drain Punch, Focus Punch, Low Sweep, and Brick Break. Not really the strongest moves.